The way I see it, pledging the guitars I'm currently constructing to keen players free of charge has a dual benefit. Not only is it a nice thing to be able to do for someone who might otherwise never own a handmade instrument, but I also get to have my guitars road tested under real-world conditions. With instructions to play the hell out of them and subject them to the rigours of everyday use, hopefully they'll take this treatment in their stride and I'll be more confident of approaching guitar building as a commercial enterprise, albeit in a limited way. Were I to keep the guitars for my own use, I'd really be none the wiser; they would see little use and, when they were played, I'd follow past practice and handle them with kid gloves. I'd rather not make the assumption that life for a guitar is always that easy! I have sold several instruments in the past, but I feel I did so in ignorance of the risks and the potential for conflict.
Having built around 15 electric and acoustic guitars over the past 20 years, I know that structurally they'll hold up just fine. The area in which I do need reassurance is with the finish I'm about to use for the first time. KTM-SV, a water-based urethane, is receiving great press from those who've tried it, but I'd like to see for myself how it stands up to use and abuse over, say, 12 to 18 months. I can extrapolate from there and make an assessment as to what the longer-term prognosis is likely to be. The manufacturer, Grafted Coatings, has this to say about KTM-SV:
KTM-SV Spar Varnish wood finish is a waterborne, oil-modified, self-crosslinking urethane system. It features high quality, low film yellowing, excellent chemical, mar and scuff resistance, and is specifically designed for finishing wood. Because of its inherent oil urethane characteristics, the user can expect excellent flow, leveling and penetration into porous wood surfaces. Applied by spray or brush, maintaining high solids in the coating allows for good film build and fewer coats to apply.
In my search for a safe, environmentally friendly finish material, I've found any number of products which sound good on paper, however, the reality is that the demands placed on a finish destined for an acoustic guitar are unique. Tops, backs and sides are in the region of 2mm to 3mm thick and expand and contract unhindered. Not only does the finish need to be wear and scuff resistant, but it must also be flexible enough to withstand these changes in dimension on a daily basis. Add to that the guitar-buying public's expectation that their prize instrument should have a mirror-like gloss and the list of candidates shrinks significantly!